1. Field of Use
The present invention relates to an apparatus and method for removing a low-viscosity hydrocarbon from a body of liquid through the employment of an endless flexible belt which absorbs the hydrocarbon from the liquid for deposit in a container. More particularly, the present invention relates to a low-viscosity hydrocarbon collector which utilizes an endless belt in a confined below-grade environment, such as a well bore, and which incorporates rollers for removal of the low viscosity hydrocarbons from the endless belt.
2. Prior Inventions
Contamination of groundwater with hydrocarbons is an important concern for all sectors of society. In order to minimize or eliminate the adverse effects of such contamination, environmental protection agencies (both state and federal) require complete removal of any hydrocarbons discovered in the groundwater. Monitoring wells located in the proximity of sites susceptible to contamination by hydrocarbons are the usual means by which groundwater purity is monitored and, in the event that contamination is discovered in a monitoring well, diligent efforts must be made to remove all of the hydrocarbons floating on the surface of the groundwater--even the monolayer sheen which indicates the presence of the slightest contamination.
However, such removal of hydrocarbons from the surface of the groundwater in monitoring wells can be quite costly and time-consuming. Significant contamination may lead to months, or even years, of diligent clean-up efforts, especially if the contamination becomes absorbed into the subsurface formations, only to be slowly leached into the groundwater.
To make matters worse, the previous options for achieving complete removal of the floating hydrocarbons have been limited, if not completely inadequate. In those situations where it is economically justifiable, floating hydrocarbons can be removed, along with the entire contents of a monitoring well, through vacuum operations; however, such operations usually require periodic evacuation of the well with a vacuum truck, sometimes as often as twice a week, for a cost of about $400 per evacuation. Automatic bailing equipment, which systematically bails the top surface of the liquid in the well, can be employed on a similar basis but, again, the equipment and/or services are expensive and the operation must be performed on a frequent basis. Moreover, both of the mentioned options are inefficient in that substantial amounts of groundwater are removed with the hydrocarbons as a matter of course, which unnecessarily increases the volume and cost of proper liquid disposal.
More sophisticated equipment, such as the patented"Filter-Scavenger" (U.S. Pat. No. 4,243,529) produced by Oil Recovery Systems, Inc., is available to separate and retrieve only the hydrocarbons from a monitoring well by filtering the hydrocarbons from the water within the well bore and then pumping the filtered hydrocarbons to the surface with a surface-mounted pump. Oil Recovery Systems, Inc. also produces a "Probe-Scavenger" system which recovers only hydrocarbons by controlling the operation of a submersible pump through the employment of a probe that differentiates between hydrocarbons and water. However, each of those systems costs about $10,000 plus installation costs and do not completely remove the monolayer sheen as required by governmental authorities.
Moreover, while the degree of contamination most often encountered is only minimal, the costs of any of the above options often make those options unjustifiable, especially for small-scale facilities. As a result, many resort to manually removing hydrocarbons from the surface of well water with commonly available polypropylene pads, which absorb low-viscosity hydrocarbons, by dropping such a pad into the well bore with a string attached, retrieving the pad with the string, wringing out the pad and then repeating the process until even the hydrocarbon sheen on the water surface is removed. In fact, the painstaking use of such pads is required even with the high-cost equipment in order to completely remove the monolayer sheen.
High-viscosity hydrocarbon skimmers, on the other hand, have long been an economical means employing endless belts for removing such hydrocarbons from the surface of larger bodies of water. For example, the U.S. Pat. No. 3,508,663, issued to Brill in 1970, discloses such a collector which drives an endless polyurethane loop through a body of water to adsorb hydrophobic materials therefrom. The hydrophobic materials are then removed from the polyurethane loop by means of a scraper and pumped into a storage container. A single motor drives both the polyurethane loop and the pump. Subsequent patents, including U.S. Pat. No. 4,274,957 issued to Koller, U.S. Pat. No. 4,582,604 issued to Bashaw, and U.S. Pat. No. 4,652,372 issued to Threadgill, teach various improvements in high-viscosity hydrocarbon skimmers.
However, employment of such hydrocarbon skimmers in the field of the present invention is unworkable for many reasons. First of all, all previous hydrocarbon skimmers operate on the principle of adsorption wherein the hydrocarbons adhere to the surface of an endless belt and are then removed therefrom by means of scrapers or rollers. Such operation is ineffective with low-viscosity hydrocarbons (i.e., hydrocarbon liquids, such as gasoline or diesel, with viscosity in the range of 1 to 40 S.U.S.) because low-viscosity hydrocarbons tend to slough (or flow) down the endless belt faster than they can be removed and collected. Additionally, even utilization of known hydrocarbon skimmers of the endless belt type for removing high-viscosity hydrocarbons from a monitoring well would require placement of the unit above an open well bore for extended periods during operation. In the meantime, any activities in the proximity of the well would have to be navigated around the skimmer, severely disrupting any business or other surface activities at the location of the well.